This study represents a continuation of ongoing work to accomplish two objectives: 1) to extend observations on approximately 50,000 male former students from Harvard and the University of Pennsylvania (and 3,500 female former students from the University of Pennsylvania) in order to identify characteristics of college youth and alumni predictive of site-specific and total cancers later in life; and 2) to develop improved quantitative methods for detecting combinations of these predictive characteristics. Physical examinations and other college records of the years 1916-1950 comprise the initial data to be examined for associations with fatal and nonfatal cancers identified on death certificates or on self-assessed mail questionnaires during a 33-67 year followup period. To date, approximately 1,800 fatal and 1,700 nonfatal cancers have occurred among these former students in nearly two million person-years of observation. The study affords a prospective perspective for both hypothesis testing and hypothesis seeking. Analytic methods include multivariate case-control and exposed-nonexposed comparisons. This ongoing study utilizes predocumented data on young adults and older alumni. Thus, unlike cross-sectional or retrospective studies, this approach avoids the need to infer previous from present behavior or to recall characteristics antecedent to cancer diagnosis.